Chair backrest



FIG. 1 is a perspective view of a chair backrest showing my new design;

FIG. 2 is a rear perspective view of the design;

FIG. 3 is a front view of the design;

FIG. 4 is a rear view of the design;

FIG. 5 is a left side view of the design;

FIG. 6 is a right side view of the design;

FIG. 7 is a top view of the design;

FIG. 8 is a bottom view of the design; and,

FIG. 9 is another perspective view of FIG. 1. The broken lines showingthe remainder of the chair are for illustrative purposes only and formno part of the claimed design.

The ornamental design for a chair backrest, as shown and described.